Solid state electronic imaging devices, such as charge coupled devices (CCD's) and the like, have been utilized in a wide variety of electronic imaging systems to generate electronic representations of an imaged scene. One common electronic image device structure, for example, is the full-frame CCD image sensor that typically includes a vertical CCD shift register containing a two dimensional array of photocapacitive sensing elements (pixels), which also serve as a photocharge transport mechanisms, a horizontal CCD output shift register formed on a silicon substrate, and an output amplifier coupled to the horizontal CCD shift register. An image is acquired by the image sensor when incident light, in the form of photons, falls on the array of pixels in the vertical CCD shift register and generates a proportional photocharge within the silicon substrate at each pixel site The photocharge is collected locally at each pixel site of the array in potential wells formed within the silicon substrate by the application of voltage or clock signals to clock lines of the vertical CCD shift register. Columns of collected photocharge are transported or shifted in parallel from the vertical CCD shift register row by row into the horizontal CCD shift register. Voltage signals are then applied to clock lines of the horizontal CCD shift register to transport or shift the rows of charge pixel by pixel from the horizontal CCD shift register to the output amplifier. The signal from the output amplifier is generally clamped and sampled at an appropriate pixel rate to generate an effective output signal that is subsequently supplied to signal processing circuitry.
Conventional electronic imaging systems, however, have been found to exhibit a non-linearity in their output response. It is an object of the invention to eliminate, or substantially reduce, this non-linearity to improve the overall output response of such systems.